mmc: slot-gpio: add gpiod variant to get wp GPIO

This makes it possible to get the write protect (read only)
GPIO line from a GPIO descriptor. Written to exactly mirror
the card detect function.
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/slot-gpio.c

@@ -325,6 +325,54 @@ int mmc_gpiod_request_cd(struct mmc_host *host, const char *con_id,
 }
 EXPORT_SYMBOL(mmc_gpiod_request_cd);
 
+/**
+ * mmc_gpiod_request_ro - request a gpio descriptor for write protection
+ * @host: mmc host
+ * @con_id: function within the GPIO consumer
+ * @idx: index of the GPIO to obtain in the consumer
+ * @override_active_level: ignore %GPIO_ACTIVE_LOW flag
+ * @debounce: debounce time in microseconds
+ *
+ * Use this function in place of mmc_gpio_request_ro() to use the GPIO
+ * descriptor API.  Note that it is paired with mmc_gpiod_free_ro() not
+ * mmc_gpio_free_ro().
+ *
+ * Returns zero on success, else an error.
+ */
+int mmc_gpiod_request_ro(struct mmc_host *host, const char *con_id,
+			 unsigned int idx, bool override_active_level,
+			 unsigned int debounce)
+{
+	struct mmc_gpio *ctx;
+	struct gpio_desc *desc;
+	int ret;
+
+	ret = mmc_gpio_alloc(host);
+	if (ret < 0)
+		return ret;
+
+	ctx = host->slot.handler_priv;
+
+	if (!con_id)
+		con_id = ctx->ro_label;
+
+	desc = devm_gpiod_get_index(host->parent, con_id, idx, GPIOD_IN);
+	if (IS_ERR(desc))
+		return PTR_ERR(desc);
+
+	if (debounce) {
+		ret = gpiod_set_debounce(desc, debounce);
+		if (ret < 0)
+			return ret;
+	}
+
+	ctx->override_ro_active_level = override_active_level;
+	ctx->ro_gpio = desc;
+
+	return 0;
+}
+EXPORT_SYMBOL(mmc_gpiod_request_ro);
+
 /**
  * mmc_gpiod_free_cd - free the card-detection gpio descriptor
  * @host: mmc host

include/linux/mmc/slot-gpio.h

@@ -25,6 +25,9 @@ void mmc_gpio_free_cd(struct mmc_host *host);
 int mmc_gpiod_request_cd(struct mmc_host *host, const char *con_id,
 			 unsigned int idx, bool override_active_level,
 			 unsigned int debounce);
+int mmc_gpiod_request_ro(struct mmc_host *host, const char *con_id,
+			 unsigned int idx, bool override_active_level,
+			 unsigned int debounce);
 void mmc_gpiod_free_cd(struct mmc_host *host);
 void mmc_gpiod_request_cd_irq(struct mmc_host *host);